TIME OF REMEDIATION ESTIMATES AT A NAPL-CONTAMINATED FRACTURED-ROCK SITE

Methods to estimate the cleanup timeframe are needed to compare remedial strategies, to meet regulatory requirements, and to optimize cost to completion. Natural Attenuation Software (NAS) is a screening tool to estimate remediation timeframes for combined remedies and to assist in decision-making on the level of source zone treatment in conjunction with monitored natural attenuation (MNA) using site-specific remediation objectives. NAS consists of a combination of analytical and numerical solute transport models implemented in three main interactive modules to provide estimates for: 1.) target source concentration required for a plume extent to contract to regulatory limits, 2.) time required for NAPL contaminants in the source area to attenuate to a predetermined target source concentration, and 3.) time required for a plume extent to contract to regulatory limits after source reduction.

The objective of this research is to estimate time of remediation at a contaminated site in which contaminants from an industrial facility have entered the upper part of a 52-m thick dolomite aquifer. Trichloroethene (TCE) and other chlorinated ethenes are present as an aqueous phase plume derived from a well-defined source of dense non-aqueous phase liquid (DNAPL). The on-going remediation strategy involves a combination of pump-and-treat and MNA. NAS simulation results suggest that while the multi-well pumping system has decreased concentrations of TCE in groundwater, the cleanup timeframe is not significantly different between MNA-only and the current strategy.